If you use the compound pulley, you will need to pull twice the distance but with less force. the force you need is equal to one half the weight of the box plus 25 N. what is the force needed?

F= 25/2 = 12.5N

Explanation:

When you use a compound pulley the force required depends on the mechanical advantage of the compound pulley. This is known as rate of loss of distance or the ratio of the force to the load.

M.A = Effort distance /Load distance. OR M.A = Load/Effort

b. lifting dumbbell weight at 20-degree angle from the body after a 45-degree angle